A storage system is a computer that provides storage service relating to the organization of information on writable persistent storage devices, such as memories, tapes or disks. The storage system is commonly deployed within a storage area network (SAN) to or a network attached storage (NAS) environment. When used within a NAS environment, the storage system may be embodied as a file server including an operating system that implements a file system to logically organize the information as a hierarchical structure of directories and files on, e.g. the disks. Each “on-disk” file may be implemented as a set of data structures, e.g., disk blocks, configured to store information, such as the actual data for the file. A directory, on the other hand, may be implemented as a specially formatted file in which information about other files and directories are stored.
The file server, or filer, may be further configured to operate according to a client/server model of information delivery to thereby allow many client systems (clients) to access shared resources, such as files, stored on the filer. Sharing of files is a hallmark of a NAS system, which is enabled because of its semantic level of access to files and file systems. Storage of information on a NAS system is typically deployed over a computer network comprising a geographically distributed collection of interconnected communication links, such as Ethernet, that allow clients to remotely access the information (files) on the filer. The clients typically communicate with the filer by exchanging discrete frames or packets of data according to pre-defined protocols, such as the Transmission Control Protocol/Internet Protocol (TCP/IP).
In the client/server model, the client may comprise an application executing on a computer that “connects” to the filer over a computer network, such as a point-to-point link, shared local area network, wide area network or virtual private network implemented over a public network, such as the Internet. NAS systems generally utilize file-based access protocols; therefore, each client may request the services of the filer by issuing file system protocol messages (in the form of packets) to the file system over the network identifying one or more files to be accessed without regard to specific locations, e.g., blocks, in which the data are stored on disk. By supporting a plurality of file system protocols, such as the conventional Common Internet File System (CIFS), the Network to File System (NFS) and the Direct Access File System (DAFS) protocols, the utility of the filer may be enhanced for networking clients.
A SAN is a high-speed network that enables establishment of direct connections between a storage system and its storage devices. The SAN may thus be viewed as an extension to a storage bus and, as such, an operating system of the storage system enables access to stored information using block-based access protocols over the “extended bus”. In this context, the extended bus is typically embodied as Fibre Channel (FC) or Ethernet media adapted to operate with block access protocols, such as Small Computer Systems Interface (SCSI) protocol encapsulation over FC or TCP/IP/Ethernet.
A SAN arrangement or deployment allows decoupling of storage from the storage system, such as an application server, and some level of information storage sharing at the application server level. There are, however, environments wherein a SAN is dedicated to a single server. In some SAN deployments, the information is organized in the form of databases, while in others a file-based organization is employed. Where the information is organized as files, the client requesting the information maintains file mappings and manages file semantics, while its requests (and server responses) address the information in terms of block addressing on disk using, e.g., a logical unit number (lun).
Fibre Channel is a set of related protocols that defines a transport mechanism for data over a network. Each Fibre Channel device (e.g., a storage adapter) connected to a network has a world wide name (WWN) comprising a node name. Typically, the node name is hard wired into the device so that it may not be modified. As each device connected to a Fibre Channel network has a unique node name, this hard encoding of the node name prevents duplicate node names from appearing on the same Fibre Channel switching fabric, which can lead to routing errors and data loss.
A noted disadvantage of the conventional hard encoding of the node name is that should a storage system be replaced, the clients of that system need to update their internal contact information as the new storage system will have a different node name. Similarly, if a storage system that is serving data to a set of original clients is taken offline and then reactivated, but with a differing set of volumes of data, the original clients may subsequently direct data access requests to the incorrect storage system. A “volume” is a cluster of physical storage devices that define an overall logical arrangement of storage space. Furthermore, if storage systems are configured as partners of a cluster and a failover situation arises such that a functioning cluster partner assumes control of the disks and manages data access requests of a failed cluster partner, a new node name will appear to be associated with that failed partner. Such a failover situation is described in U.S. Pat. No. 7,260,737, entitled SYSTEM AND METHOD FOR TRANSPORT-LEVEL FAILOVER OF FCP DEVICES IN A CLUSTER, by Arthur Lent, et al., issued on Aug. 21, 2007, the contents of which are hereby incorporated by reference.
The disadvantages described above are more noticeable when individual network interface controllers (NICs) or host bus adapters (HBAs) of a given storage system are replaced or swapped. As node names are often assigned to certain HBAs or NICs, the changing of a HBA/NIC results in a modified node name for a given storage system. A similar problem arises when a HBA/NIC is then moved from an original storage system to a second storage system. Clients of the original storage system thereafter direct their data access requests to the second storage system, which is not adapted to accept or process these data access requests.
Thus, use of conventional, hard-coded, WWNs as node names in various network configurations may result in additional client-side configuration issues to manage in order to permit the clients to continue to properly access data stored on a storage system. Such client-side configuration is rather burdensome and, therefore, undesirable.